JPH05327182A - Method for managing electrodeposition resist bath - Google Patents

Abstract

PURPOSE:To refine a negative electrodeposition bath without impairing economy and productivity by titrating the bath with acid, sensing deterioration degree of the bath with a measured value of a change ratio of a titration curve at an end point of the titration, and purifying the deteriorated bath. CONSTITUTION:A negative electrodeposited resist bath is titrated with acid, and a change rate DELTAE/DELTAT of a titration curve at an end point of the titration is measured. When the bath is deteriorated and organic acid of impurity is contained, multistage neutralization reaction is exhibited, and the change ratio of the curve at the end point is reduced. Accordingly, deterioration of the bath is sensed according to a measured value of the change ratio of the curve at the end point of the titration, and part or entirety of the deteriorated bath is purified based on its result. Thus, purification of the bath can be effectively conducted without impairing economy and productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an electrodeposition resist bath used in a printed wiring board manufacturing process.

[0002]

2. Description of the Related Art In an electrodeposition resist method for forming a resist film by an electrodeposition coating method, management of an electrodeposition bath is extremely important. Usually, the wiring board is manufactured by the electrodeposition resist method by the following process.

Degreasing of substrate → washing → pickling → washing → electrodeposition →
Washing → drying → exposure → development → etching → resist film peeling Then, in order to increase the utilization rate of the solid content of the electrodeposition bath, a part of the electrodeposition bath is subjected to ultrafiltration, and the high solid content electrodeposition solution is electroplated The filtrate (hereinafter, referred to as “ultrafiltrate”) returned to the electrodeposition tank is used as a cleaning liquid for collecting the solid content of the electrodeposition bath adhering to the electrodeposition substrate. Further, in order to keep the solid content concentration of the electrodeposition bath constant, the amount of the electrodeposition bath consumed by electrodeposition is replenished. Water balance is maintained by purging the ultrafiltrate.

However, when long-term continuous electrodeposition is carried out, the acid component of the pickling solution or the hydrolysis product of the resist component, especially the organic acid, accumulates in the electrodeposition bath. As a result, the elution of copper from the copper-clad substrate is promoted, the properties of the electrodeposition coating film deteriorate, and in the worst case, the resist film develops poorly.

In order to avoid such troubles, in the past, 1) when an abnormal coating film such as poor development occurs, a large amount of the ultrafiltrate in the electrodeposition bath is discarded, and a considerable amount of the simulated filtrate is transferred to the electrodeposition bath. Supply. 2) A part of the ultrafiltrate of the electrodeposition bath is always discarded, and a considerable amount of the simulated filtrate is supplied to the electrodeposition bath. Such a bath management method was adopted. However, these methods are insufficient in terms of economical efficiency or productivity.

[0006]

In the conventional bath control method, the concentration of impurities in the electrodeposition bath, which adversely affects the properties of the electrodeposition coating film, is not clearly grasped, so that the bath is excessively refined, or There was a tendency to have inconvenience that it was too late to respond. This is because the concentration of impurities in the electrodeposition bath, which is an indicator of bath deterioration, or the amount having a primary relationship with the concentration is not known.

The concentration of impurities in the electrodeposition bath is determined by analyzing the ultrafiltrate by liquid chromatography. However, this method has the limitation that it takes a long time to stabilize the equipment or that the column must be maintained and managed with great care.Therefore, this method is not suitable as a process analysis method that requires swiftness. Hard to say. If there is a simpler method to detect the impurity concentration in the electrodeposition bath,
Bath management will be easier and more economical to implement.

[0008]

Means for Solving the Problems The inventors of the present invention have made earnest studies on a method for detecting the concentration of impurities in an electrodeposition bath. As a result, the titration at the end point when the electrodeposition bath was titrated with an acid for amine value measurement. We know that there is a significant correlation between a decrease in the rate of change of the curve ΔE / ΔT (where E is the potential or pH and T is the titer) and an increase in the concentration of impurities in the electrodeposition bath. It was That is, the inventors have learned that the rate of change of the titration curve at the end point can be an index of bath deterioration and have completed the present invention.

That is, according to the present invention, the negative electrodeposition resist bath is titrated with an acid, and the change rate ΔE of the titration curve at the end point of the titration.
The method for controlling an electrodeposition resist bath is characterized in that the degree of deterioration of the bath is detected from the measured value of / ΔT and a part or the whole of the deteriorated bath is purified.

The end point of titration is ΔE / ΔT in the titration.
Is the maximum value, that is, the point where the change of the characteristic value such as the potential is the sharpest in the titration curve. ΔE is the change in the characteristic value of the titration solution and is usually expressed by the change in the potential when an automatic titrator is used, but it is the change in the pH as when a titration curve is created using a pH meter or the like. May be represented.

In the present invention, the method of titrating the electrodeposition bath with an acid may be an ordinary method. For example, a sample of the electrodeposition bath is dissolved in acetone and the acetone solution is titrated with dilute hydrochloric acid. At this time, 50 to 100 cc for 2 g of sample
It is preferable to titrate the above acetone solution with 0.1N hydrochloric acid because the change in the titration curve at the end point of the titration becomes sharp. If you use an automatic titrator for titration,
It is preferable because the rate of change of the titration curve at the end point of titration can be automatically measured.

The rate of change of the titration curve at which the bath is to be purified or discarded depends on the properties of the target electrodeposition coating film and the type of bath and cannot be generally stated. Usually, the titration of the electrodeposition bath and the creation of the evaluation substrate are continuously performed once, and the rate of change of the titration curve allowed from the properties of the electrodeposition coating film of the obtained substrate is determined. The method of managing the bath is taken as a guide.

As a method of purifying the bath, a method of passing it through an ion exchange resin column is generally used. In this case, there are a method of passing the electrodeposition bath itself and a method of passing the limiting filtrate, but the latter method is preferable because the ion exchange resin in the column can be easily regenerated. As another method for purifying the bath, there is a method of discarding a part of the electrodeposition bath or a part or all of the limiting filtrate and supplying a new electrodeposition bath or a simulated filtrate to the electrodeposition tank.

[0014]

The reason why the rate of change of the titration curve at the end point correlates with the impurity ion concentration is presumed to be as follows.

In the acrylic polymer composed of acrylic acid and its derivatives, the carboxyl group exists in a state of being suspended in the main chain, so that dissociation of the carboxyl group into protons is suppressed for electrostatic reasons. That is, the carboxyl group in the acrylic polymer will behave as an acid weaker than the carboxyl group of the acrylic acid monomer.

As a result, when a solution in which salts of acrylic acid and other organic acids and salts of an acrylic polymer coexist, is titrated with an acid, the carboxylate of the acrylic polymer reacts with a proton in a region close to neutral, and the reaction After that, the carboxylates of acrylic acid and other organic acids will react with protons in a more acidic region. That is, such a sample solution exhibits a multistage neutralization reaction, and the rate of change of the titration curve at the end point is smaller than that in the case where only the acrylic polymer is present.

Since the dissociation constant into protons varies depending on the type of organic acid to be accumulated, the more kinds of organic acid to accumulate, the more gently the titration curve becomes, and the smaller the rate of change of the titration curve near the end point.

[0018]

EXAMPLES The present invention will be described in more detail below with reference to examples. (Preparation of electrodeposition bath) 45 parts by weight of methyl methacrylate (parts by weight; the same applies hereinafter), 20 parts of isobutyl acrylate,
15 parts of hydroxyethyl methacrylate, acrylic acid 2
A mixed solution of 0 part and 2 parts of azobisisobutyronitrile was added dropwise to 110 parts of isopropyl alcohol kept at a temperature of 80 ° C. under a nitrogen atmosphere over 5 hours. Then, the mixture was aged for 1 hour, and then azobisisobutyronitrile 0.
5 parts and 10 parts of isopropyl alcohol were added and aged for 2 hours to synthesize a high acid value acrylic resin solution.

While blowing air into this high acid value acrylic resin solution, 20 parts of glycidyl methacrylate, 0.7 part of dimethylbenzylamine as a catalyst and 0.15 part of phenothiazine were added and reacted at a temperature of 80 ° C. for 12 hours to give a high temperature. An acid value photosensitive resin solution was obtained. The nonvolatile component in this high acid value photosensitive resin solution was 50% by weight, the acid value was 74, the number average molecular weight of the high acid value photosensitive resin was 38,000, and the unsaturated equivalent was 1 mol / kg.

To 138 parts of this high acid value photosensitive resin solution, 33 parts of trimethylolpropane triacrylate and 5 parts of Irgacure 907 (manufactured by Ciba-Geigy: α-aminoacetophenone) as a photoinitiator were added and mixed well. 6 parts of triethylamine to neutralize
Add deionized water to a solids content of 15%,
A negative type anionic electrodeposition coating (pH 7.1) was obtained.

(Preparation of Test Substrate) A copper clad laminate (40 × 150 ×) for printed wiring board was prepared by using the above electrodeposition paint.
1.6 mm) as an anode and a SUS304 plate as a cathode, the coating temperature was set at 25 ° C., the current value was set to a current density of 60 mA / dm ^2, and current was applied for 3 minutes to perform electrodeposition coating. After electrodeposition, the copper clad laminate having the coating film deposited thereon is washed with water, air-dried with an air knife, and then heated and dried at a temperature of 100 ° C. for 5 minutes,
A smooth, non-tacky photoresist film having a thickness of 18 μm was obtained.

Next, a wiring pattern film having various intervals was adhered on the photoresist film by a vacuum device, and an irradiation dose of 10 was applied using an ultrahigh pressure mercury lamp of 3 kW.
Exposure was performed at 0 mJ / cm ² . Subsequently, after developing with a 1% sodium carbonate aqueous solution, etching is performed with a ferric chloride aqueous solution, and the remaining resist film is removed with a 3% sodium hydroxide aqueous solution to obtain a printed wiring board (test board) having a wiring pattern. It was

(Measurement of amine value of electrodeposition bath) 2 g of the electrodeposition bath was sampled, acetone was added to make a uniform solution of 70 cc, and titration was performed using 0.1N hydrochloric acid standard solution. The titrator is the Hiranuma Sangyo Co., Ltd. automatic titrator Comtite-9.
00 was used, and the end point of the titration was determined by the inflection point method.

(Example 1) An electrodeposition bath was placed in an electrodeposition apparatus, the bath temperature was kept at 25 ° C, and the pH, conductivity, and titration curve of the electrodeposition bath were measured at regular intervals, and an evaluation substrate was prepared. Then, the performance of the electrodeposition bath was investigated. Then, the deterioration bath was purified by an anion exchange resin. As the anion exchange resin, a strongly basic anion exchange resin DIAION SA-10AP manufactured by Mitsubishi Kasei Co., Ltd. was used, and the electrodeposition bath was passed through the column at SV10 ^-1 . The results are shown in Table 1. In addition, the pattern formability is what was evaluated by a scanning electron microscope to see how far the wiring pattern is developed,
The line indicates the portion where the resist film remains, and the space indicates the portion where the resist film does not exist.

[0025]

[Table 1] (Unit) Conductivity: μS / cm Pattern formability: Line (μm) / Space (μm) Change rate: ΔE / ΔT (mV / ml) at end point

(Example 2) An electrodeposition bath was placed in an electrodeposition apparatus, the bath temperature was kept at 25 ° C, and a titration curve of the electrodeposition bath was measured and an evaluation substrate was prepared at regular intervals of time. I investigated the performance of. The rate of change at the end of titration is 100
When it became 0 or less, the electrodeposition bath was passed through the same anion exchange resin column as in Example 1 for purification. By continuing this operation, the pattern formability of 50 μm / 50 μm could be maintained for at least 3 months.

(Example 3) An electrodeposition bath equipped with an ultrafiltration device was filled with an electrodeposition bath, the bath temperature was kept at 25 ° C, and a titration curve of the electrodeposition bath was measured and evaluated at regular intervals. Was prepared and the performance of the electrodeposition bath was investigated. The ultrafiltration module is UFD-10-MPL-LT manufactured by Yuasa Battery Co., Ltd.
, The module inlet pressure is 1.9 kg / cm ² ,
The outlet pressure was 1.0 kg / cm ² . When the rate of change at the titration end point was 1000 or less, the simulated filtrate was supplied to the electrodeposition tank while the ultrafiltrate was discarded to purify the bath. By continuing this operation,
The patternability of 50 μm / 50 μm could be maintained for at least 3 months.

(Example 4) An electrodeposition bath equipped with an ultrafiltration device was filled with an electrodeposition bath, the bath temperature was kept at 25 ° C, and a titration curve of the electrodeposition bath was measured and evaluated at regular intervals. Was prepared and the performance of the electrodeposition bath was investigated. Then, when the rate of change at the titration end point was 1000 or less, the bath was purified by passing the ultrafiltrate through an anion exchange resin column that was branched and attached to the ultrafiltrate outlet pipe. By continuing this operation, pattern formability of 50 μm / 5
It was possible to maintain 0 μm for at least 3 months.

[0029]

INDUSTRIAL APPLICABILITY The electrodeposition bath control method of the present invention is capable of easily detecting the degree of deterioration of the electrodeposition bath and effectively purifying the bath by applying a normal bath control process analysis method. is there. Therefore, according to the present invention, the purification of the bath can be carried out economically and without impairing the productivity, so that it has a great advantage in practical use.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area G03F 7/16

Claims (1)

[Claims] 1. A negative electrodeposition resist bath is titrated with an acid, and the rate of change of the titration curve at the end of titration is ΔE / ΔT (where ΔE is the change in potential or pH, and ΔT is the titer). The degree of deterioration of the bath is detected based on the measured value of), and a part or the whole of the deteriorated bath is purified to control the electrodeposition resist bath.